100 ARNOLD W. COOPER. 



Thoracic Appendages. 



First pair. — First thoracic appendages: Basipodite 

 two-jointed; Exopodite three-jointed; first and third joints 

 provided on the outer edge each with a short seta bearing 

 four or five short spines; no seta present on the second joint; 

 the inner edge of the third joint is provided with six phimous 

 bristles ; the terminal two serrated on the outer edge. 

 Endopodite two-jointed; setaj absent on the outer edge; 

 the inner edge bears seven long plumous bristles (fig. 11). 



Second, third, and fourth pair. — Basipodite two 

 ^joints ; Exopodite three joints, each bearing on the outer 

 edge a swollen seta with spines ; on the inner edge seven 

 plumous bristles and a terminal serrated seta. Endopodite 

 three joints, bearing along- the outer edge and terminally 

 ten plumous bristles (fig. 12). 



Fifth pair. — Male asymmetrical, the right appendage 

 being the larger, consisting of (1) Basipodite with two 

 joints, (2) Exopodite, two-jointed; the second joint with a 

 small spine on the outer edge, and long terminal curved claw 

 without serrations. Endopodite three - jointed without 

 bristles. Left : Exopodite not obviously jointed off from 

 Basipodite, bearing on the inner edge two smooth pads or 

 cushions ; no " appendage " present on the outer edge ; two 

 claws, the outer being the larger. No endopodite has been 

 observed (fig. 13). 



Female, — Right and left symmetrical. Basipodite two- 

 jointed, Exopodite tAvo-jointed, the second joint bearing a 

 prominent claw serrated on the inner edge; the place -of the 

 third joint is occupied by a prominent spine (.y.), two accessory 

 spines [a. s.) on the posterior surface. Endopodite one 

 joint, with two terminal stout spines (fig. 14). 



Systematic Position. 



The characters in which the present species agrees with 

 Diaptomus are numerous, and it is scarcely necessary to 

 enumerate them ; the characters in which it differs are : 



